Rajat Saxena

Congratulations Roxana! I hope you had a fun celebration

My PhD journey has officially come to end with a Summa Cum Laude, thanks to all the amazing people who’ve supported me along the way, especially my advisors Anna Levina and @engeltatiana.bsky.social!
Which apparently coincided with graduation from a witchcraft and wizardry school 😉

#neuroskyence

This is a super interesting paper from Bruce McNaughton’s lab, showing why we should study behavior in the context of natural/ecological environments. They show that living in enriched complex environments, prior to task performance, affects both behavior and the underlying neural activity.

Representational drift without synaptic plasticity Neural computations support stable behavior despite relying on many dynamically changing biological processes. One such process is representational drift (RD), in which neurons' responses change over ...

When neurons change, but behavior doesn’t: Excitability changes driving representational drift

New preprint of work with Christian Machens: www.biorxiv.org/content/10.1...

Variations in neuronal selectivity create efficient representational geometries for perception Our visual capabilities depend on neural response properties in visual areas of our brains. Neurons exhibit a wide variety of selective response properties, but the reasons for this diversity are unkn...

In many brain areas, neuronal tuning is heterogeneous. But how does this diversity help behavior? We show how tuning diversity shapes representational geometry and boosts coding efficiency for perception in our new preprint: www.biorxiv.org/content/10.1...
(w/ @sueyeonchung.bsky.social&Tony Movshon)

A new study led by @timothysit.bsky.social reveals that different layers of mouse V1 integrate visual and non-visual signals differently.

Activity is dominated by vision (or spontaneous fluctuations) in L2/3 and by movement in L5. This leads to different geometries.
www.biorxiv.org/content/10.1...

I'm pleased to share our new work, “Spatio-temporal organization of network activity patterns in the hippocampus”, out in @cp-cellreports.bsky.social !
With Demi Brizee & David Dupret, we track how oscillations and spiking behaviour map onto hippocampal layers using an LFP-based embedding.

(1/13)

Congratulations! 🎉

Direct entorhinal control of CA1 temporal coding Nature Communications - Temporal coding in the hippocampus is thought to be key for memory and predictions. Here, the authors show that blocking one entorhinal input affects two aspects of...

Our collaboration - from PhD work - examining input-specific (EC L3) contributions to rate and temporal coding in CA1 place cells is now out in @natcomms.nature.com 🔬🧠

rdcu.be/evWtz

Dopamine encodes deep network teaching signals for individual learning trajectories Longitudinal tracking of long-term learning behavior and striatal dopamine reveals that dopamine teaching signals shape individually diverse yet systematic learning trajectories, captured mathematical...

Super excited to see this paper from Armin Lak & colleagues out! (I've seen @saxelab.bsky.social present it before.)

www.cell.com/cell/fulltex...

tl;dr: The learning trajectories that individual mice take correspond to different saddle points in a deep net's loss landscape.

🧠📈 🧪 #NeuroAI

Our study is out in Nature!
Using wireless Neuropixels we recorded hippocampal activity in freely flying bats and uncovered replay and theta(less) sweeps, revealing striking differences from classic rodent models.

👉 www.nature.com/articles/s41...

Power Pixels: a turnkey pipeline for processing of Neuropixel recordings There are many open-source tools available for the processing of neuronal data acquired using Neuropixels probes. Each of these tools, focuses on a part of the process from raw data to single neuron a...

Do you do Neuropixel recordings and are you struggling with preprocessing? The Power Pixels pipeline is an easy-to-use pipeline from raw data to neural activity of single neurons in specified brain regions 🧠 Now on bioRxiv!
www.biorxiv.org/content/10.1...

We observed that hippocampal SWRs arriving near the Down-to-Up or Up-to-Down transitions of the sleep slow oscillations (SO) can entrain novel memory replay in cortex, while the middle phase of the Up state tends to replay familiar cortical memories.

Our work with Maxim Bazhenov's group showing interleaved replay of new and old memories within individual Up states using a combination of biophysical modeling and electrophysiology experiments.

Event structure sculpts neural population dynamics in the lateral entorhinal cortex Our experience of the world is a continuous stream of events that must be segmented and organized at multiple timescales. The neural mechanisms underlying this process remain unknown. In this work, we...

Your brain doesn’t just passively track time ⏳ - it structures it.
In @Science.org we show that activity in 🧠 memory circuits (LEC) drifts constantly, but makes sharp jumps at key moments, segmenting life into meaningful events. (1/2)

👉 www.science.org/doi/10.1126/...

Our new paper out now in Science explores how neural activity in the lateral entorhinal cortex (LEC) *drifts* over time - and *jumps* at key boundaries - to help organize events in memory.

🔗 www.science.org/doi/10.1126/...

Here's a quick summary of what we found 🧵👇

Your brain learns for you even when you're not actively learning. Maybe. (in mice).

Wassifier/MergedClassifier.ipynb at master · rajatsaxena/Wassifier spike sorting cluster classifier. Contribute to rajatsaxena/Wassifier development by creating an account on GitHub.

Thanks for compiling the list. At some point, Marius and I were working on building ML models combining spatio-temporal waveform profile and autocorrelogram for unit classification as good/mua vs noise. Never finished integrating it into the KS pipeline

github.com/rajatsaxena/...

Kilosort4 detects a LOT of neurons, I recorded 15k neurons in one year 🤯 Traditionally, one would curate these detected units to see if they are well isolated single neurons. This is not feasible anymore, so today let's look at three options that are out there to automate this process! 🤖👇

I Fell Asleep While Driving, Which Led to This Diagnosis This health condition is often overlooked in women.

Over the past few years, I’ve shared my personal journey as a sleep scientist living with sleep apnea with other scientists and students to raise awareness and reduce stigma. I’m excited to reach an even broader audience in my recent interview with Parade 🎉

parade.com/health/i-fel...

The Hippocampus Book Abstract. The Hippocampus Book investigates the structure, function and pathology of the hippocampus and related cortical areas. It highlights the importan

As I transition over to Bluesky I have to plug our new #book. If you haven't already, check out the 2nd edition of The #Hippocampus Book!

academic.oup.com/book/59509?s...

Awake replay: off the clock but on the job Hippocampal replay is widely thought to support two key cognitive functions: online decision-making and offline memory consolidation. In this review, we take a closer look at the hypothesized link bet...

New opinion paper in @cp-trendsneuro.bsky.social with Dan Bendor, where we argue that rodent studies provide only marginal support for the idea that replay supports real-time decisions (e.g. planning). Fictive learning and memory tagging are more consistent w/evidence. www.cell.com/trends/neuro...

Stereo olfaction underlies stable coding of head direction in blind mice - Nature Communications Stereo olfaction involves comparing odor differences between the two nostrils. Here, using neuronal recordings and a behavioral test, the authors demonstrate that blind mice use stereo olfaction to fo...

Excited to share the sequel to our 2022 paper! In this follow-up, we show that the stable head direction (HD) signals we reported in blind mice rely on stereo olfaction—that is, the comparison of odor info. between the two nostrils.

Link: www.nature.com/articles/s41...

🧵highlights below

We're bringing together leading researchers from top institutions worldwide to Split, Croatia this summer. If you're passionate about brain-inspired AI, computational neuroscience, or fundamental mathematical principles driving intelligence, this conference is the place to be!

Many of us use 2p scopes to image 3D volumes of brain. But then we analyze the data plane by plane, resulting in duplicated neurons, missed neurons, and low s/n. Let's go 3D!

Suite3D: Volumetric cell detection for two-photon microscopy
by @haydari.bsky.social & team.
www.biorxiv.org/content/10.1...

Theoretical Neuroscience: Understanding Cognition Theoretical Neuroscience: Understanding Cognition: 9781032604824: Medicine & Health Science Books @ Amazon.com

Finally a new textbook for theoretical neuroscience. Xiao-Jing Wang wrote a nice book with very broad coverage of the field. Highly recommend. www.amazon.com/Theoretical-...

Synaptic architecture of a memory engram in the mouse hippocampus Memory engrams are formed through experience-dependent plasticity of neural circuits, but their detailed architectures remain unresolved. Using three-dimensional electron microscopy, we performed nano...

"How are memories formed and stored in the brain?...Long-term memory acquisition was found to be associated with a selective increase in multisynaptic boutons..". Groundbreaking new study from my friend and colleague Anton Maximov's lab: www.science.org/doi/10.1126/...
Bonus: My son Luca's first pub

Mathematical Methods in Computational Neuroscience Summer school in Eresfjord, Norway (July 8th - 26th, 2024)

Applications are open for the summer school 𝗠𝗮𝘁𝗵𝗲𝗺𝗮𝘁𝗶𝗰𝗮𝗹 𝗠𝗲𝘁𝗵𝗼𝗱𝘀 𝗶𝗻 𝗖𝗼𝗺𝗽𝘂𝘁𝗮𝘁𝗶𝗼𝗻𝗮𝗹 𝗡𝗲𝘂𝗿𝗼𝘀𝗰𝗶𝗲𝗻𝗰𝗲.
compneuronrsn.org

Application deadline: March 31, 2025
Located in beautiful Eresfjord, Norway 🇳🇴

#Neuroscience #ComputationalNeuroscience #KavliNeuro
@kavlintnu.bsky.social

Hippocampal Ripple Diversity organises Neuronal Reactivation Dynamics in the Offline Brain Hippocampal ripples are highly synchronized neuronal population patterns reactivating past waking experiences in the offline brain. Whether the level, structure, and content of ripple-nested activity ...

Exciting new paper from David Dupret's lab, showing that hippocampal CA1 ripples can be categorized in 2 types, either driven by CA3 or entorhinal inputs, & are associated with different replay content.
The categorization only requires pyramidal layer recording.

www.biorxiv.org/content/10.1...

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